Somatosensory evoked potentials and their relation to microstructural damage in patients with multiple sclerosis-A whole brain DTI study

Jan Hamann; Barbara Ettrich; Karl Titus Hoffman; Florian Then Bergh; Donald Lobsien

doi:10.3389/fneur.2022.890841

Somatosensory evoked potentials and their relation to microstructural damage in patients with multiple sclerosis-A whole brain DTI study

Front Neurol. 2022 Aug 29:13:890841. doi: 10.3389/fneur.2022.890841. eCollection 2022.

Authors

Jan Hamann¹, Barbara Ettrich², Karl Titus Hoffman¹, Florian Then Bergh², Donald Lobsien^{1

3}

Affiliations

¹ Institute of Neuroradiology, University of Leipzig, Leipzig, Germany.
² Department of Neurology, University of Leipzig, Leipzig, Germany.
³ Institute of Diagnostic and Interventional Radiology and Neuroradiology, Helios Klinikum Erfurt, Erfurt, Germany.

Abstract

Introduction: Somatosensory evoked potentials (SSEP) play a pivotal role in the diagnosis and disease monitoring of multiple sclerosis (MS). Delayed latencies are a surrogate for demyelination along the sensory afference. This study aimed to evaluate if SSEP latencies are representative of demyelination of the brain overall, by correlating with cerebral microstructural integrity as measured by Magnetic resonance (MR) diffusion tensor imaging (DTI). Analysis was performed in a hypothesis-free whole brain approach using tract-based spatial statistics (TBSS).

Material and methods: A total of 46 patients with MS or clinically isolated syndrome were included in the study. Bilateral SSEPs of the median nerve measuring mean N20 latencies (mN20) and Central Conduction Time (CCT), were acquired. MRI scans were performed at 3T. DTI acquisition was done with a single-shot echoplanar imaging technique with 80 diffusion directions. The FSL software package was used to process the DTI datasets and to calculate maps of fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD). These maps were then further analyzed using the TBSS module. The mean N20 and CCT and the right- and left-sided N20 and CCT were separately correlated to FA, AD, and RD, controlled for age, gender, and EDSS as variables of non-interest.

Results: Widespread negative correlations of SSEP latencies with FA (p = 0.0005) and positive correlations with RD (p = 0.0003) were measured in distinct white matter tracts, especially the optic tracts, corpus callosum, and posterior corona radiata. No correlation with AD was found in any white matter tract.

Conclusion: Highly significant correlations of FA and RD to SSEPs suggest that their latency is representative of widespread microstructural change, and especially demyelination in patients suffering from MS, reaching beyond the classic somatosensory regions. This points to the usefulness of SSEPs as a non-invasive tool in the evaluation of microstructural damage to the brain.

Keywords: MRI; diffusion tensor imaging (DTI); multiple sclerosis; sensible tract; somatosensory evoked potential (SSEP).